The present invention relates to a system for dispensing fluid from a container, in particular beer kegs.
In systems for dispensing pressurized fluid from a container, such as beer from a keg, a valve assembly is secured in the top of the container for providing access to the fluid. This valve assembly is mounted in a receiving member, generally referred to as a neck, that is secured within the only opening in the container. The valve assembly generally includes a dual valve arrangement with a siphon tube extending from the valve assembly to the bottom of the container. In operation, a gas is forced into the container through one of the valves in the valve assembly and the fluid within the container travels up through the siphon tube and out of the second valve of the valve assembly.
When employing such a fluid container, the container is formed with the neck and valve assembly mounted therein. The container is then filled with fluid and transported to the site at which the fluid is to be dispensed, such as at a tavern when the container is a beer keg. At the dispensing location, a coupler is connected to the neck. A pressure source, such as a pressurized gas is fed into one opening in the coupler and down through the first valve into the container. As the container is pressurized the fluid passes through the siphon tube and out of the second valve where it then travels through the coupler to the fluid dispensing mechanism, by a beer tap. Typically, the pressurized gas employed in such a system is carbon dioxide.
In order for such a system to work, it is mandatory that an effective seal be provided to prevent the pressurized gas being fed into the container from escaping through the neck member. For this purpose, an elastomeric O-ring is mounted in sealing engagement between the neck and a valve body portion of the valve assembly. This O-ring prevents leakage through the interface between the valve assembly and the neck. In order to achieve this seal, the O-ring is compressed between the metal shoulders of the valve body portion and the neck member. Prior to the development of the present invention and those inventions disclosed in the above-noted patent applications, the metal shoulders of the valve body portion and the neck were moved toward each other for compressing the O-ring by a threaded engagement between the valve body portion and the neck member. More specifically, the valve body portion was positioned within the neck member and rotated therein so that by additional rotation more thrust was applied against the seal since the two metal shoulders were forced closer together. The use of such a connection was apparently done on the premise that under such a force the seal continues to be compressed. However, there is a limitation as to how far the seal can be compressed without causing damage to the seal, since most elastomeric seals have a maximum compression capability of something less than ten percent of the compressed dimension. Generally, the greater the compressability, the greater the tendency of the seal to take a compression set. In other words, if an elastomeric material that has a compression limit of ten percent and is compressed from a one inch dimension to 0.9 inches and held there in that compressed mode for a sustained period of time, such a seal will not return to its original one inch dimension. Instead, such a seal might return to a new uncompressed dimension of 0.92 inches. In order to compensate for this problem, those neck and valve assemblies previously known typically allowed for an additional thrust to be created by additional rotation of the members relative to each other. Thus a very broad variation in the metal-to-metal surface dimension clearance existed since the members were merely threaded or unthreaded so as to reduce or increase the lineal dimension between the sealing surfaces.
The problem with such an approach, however, is that there is no effective way to limit the compressional forces applied to the elastomeric O-ring. Without such a limitation, the sealing ring is often overcompressed thereby subjecting it to compression set in which case it will not return to its original uncompressed state when the lineal thrust is reduced. Over a long period of time, this creates a tendency for the O-ring to lose its sealing characteristics. In addition, the O-ring can be damaged by the action of the metal shoulders rotating against the surface of the ring thereby destroying its sealing properties.
In addition to the possible loss in the efficacy of the seal, due to overcompression or damage caused by the rotation of the two metal parts, there are other substantial drawbacks to the employment of such a threaded connection. During utilization of the dispensing system, the threaded members can be loosened thereby causing the seal to be inadvertently violated. This possibility is especially significant since the coupler is typically attached to the neck member on the container by a rotational movement. Thus, the screwing and unscrewing of the coupler to the neck member can cause the threaded members to be unscrewed thereby relieving the lineal thrust applied to the O-ring and violating the seal.
The valves of the valve assembly are normally biased into their closed positions. The forces for biasing such valves are created by heavy-duty, helical springs. The creation of such forces for closing the valves leads to an additional problem when utilizing a threaded connection between the valve body portion and the neck member for holding the valves within the container. As previously mentioned, it is possible for this threaded connection to become unscrewed. If either inadvertently or by someone tampering with the dispensing system, the valve body portion that was threaded into the neck member for compressing the seal is completely unscrewed from the neck member, the force created by the springs for closing the valves will act in effect as a propulsion mechanism. Thus, if the valve body portion is accidently or through improper tampering unscrewed from the neck, without the proper precautions being taken, the valve assembly is turned into a projectile by the forces created by the springs, which can cause serious injury and possibly even death to a person standing next to the container.
Most valve assemblies used with pressurized fluid containers have included a dual valve system having two valve members, each being biased into engagement with its respective valve seat, as briefly referred to above. Typically, the helical spring for biasing at least one of the valve members circumscribes the siphon tube being utilized. A spring retaining cup is employed to hold the helical spring in place with sufficient compression to maintain the valve in a normally closed position. The cup extends downwardly from the valve body about the helical spring and has a radially projecting surface extending inwardly toward the siphon tube to support the bottom of the spring. When utilizing the helical spring in such a manner, it becomes difficult to clean and allows residue to build up in the spring coils. Because the cleaning fluids are injected under pressure through the valves, the location of the helical spring adjacent the siphon tube is one which is not readily accessible to the path taken by the pressurized cleaning fluid. In addition, the coils of the spring are not sufficiently exposed so as to receive the full effect of the cleaning fluid. The build up of residue in this area can adversely affect the quality of fluid within a container.
The build up of residue also can occur in many other locations where there are exposed crevices on the outside of the container or where there are portions inside the container that are not capable of being properly cleaned. One such possible area on the outside of the container is the recess normally provided in the neck between the top of the neck and the top of the valve assembly. This recess is typically provided in order to enable a coupler to be secured to the interior of the neck and to extend down into the neck when connected to the container.
While in the specific embodiments described herein reference is made to the container being a keg and the fluid therein being beer, the container can be used for other fluids. For example, the container can be utilized for agricultural chemicals such as pesticides, insecticides, fertilizer, etc.